SYNOPSIS

DESCRIPTION

The config_intrhook_establish() function schedules a function to be run
after interrupts have been enabled, but before root is mounted. If the
system has already passed this point in its initialization, the function
is called immediately.
The config_intrhook_disestablish() function removes the entry from the
hook queue.
Before root is mounted, all the previously established hooks are run.
The boot process is then stalled until all handlers remove their hook
from the hook queue with config_intrhook_disestablish(). The boot
process then proceeds to attempt to mount the root file system. Any
driver that can potentially provide devices they wish to be mounted as
root must use either this hook, or probe all these devices in the initial
probe. Since interrupts are disabled during the probe process, many
drivers need a method to probe for devices with interrupts enabled.
The requests are made with the intr_config_hook structure. This
structure is defined as follows:
struct intr_config_hook {
TAILQ_ENTRY(intr_config_hook) ich_links;/* Private */
void (*ich_func)(void *arg); /* function to call */
void *ich_arg; /* Argument to call */
};
Storage for the intr_config_hook structure must be provided by the
driver. It must be stable from just before the hook is established until
after the hook is disestablished.
Specifically, hooks are run at SI_SUB_INT_CONFIG_HOOKS(), which is
immediately after the scheduler is started, and just before the root file
system device is discovered.

RETURNVALUES

A zero return value means the hook was successfully added to the queue
(with either deferred or immediate execution). A non-zero return value
means the hook could not be added to the queue because it was already on
the queue.